type casting bpchar

Dear all,

I want to alter a table by creating a similar temporary table with my
modifications and inserting the values of the old table, but I get the
error message:

ERROR: Attribute 'tag' is of type '_bpchar' but expression is of type 'bpchar'
You will need to rewrite or cast the expression

Question is how do I do this, because when I write the offending value
as tag::_bpchar, I get:

ERROR: Cannot cast type 'bpchar' to '_bpchar'

This seems to be a dilemma which I don't know how to solve. I hope
someone can help me.

Greetings,
joachim

--
Dr. Joachim Trinkwitz email: jtr(at)uni-bonn(dot)de
Germanistisches Seminar phone: 0228-737565
Rheinische Friedrich-Wilhelms-Universitaet fax: 0228-737479
Am Hof 1d, 53113 Bonn, Germany web: http://www.germanistik.uni-bonn.de/jtr/